Circuit breaker with sealing means at handle-opening



Oct. 28, 1969 J ELLSWORTH ET AL 3,475,710

CIRCUIT BREAKER WITH SEALING MEANS AT HANDLE-OPENING Filed June 23, 1967 2 Sheets-Sheet l lOl FIG-6.

FIG. 7.

FIG.4.

INVENTORS James P. Ellsworth 0nd Glenn'R. Thomas WITNESSES ATTORNEY United States Patent 3,475,710 CIRCUIT BREAKER WITH SEALING MEANS AT HANDLE-OPENING James P. Ellsworth and Glenn R. Thomas, Beaver, Pa.,

assignors to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed June 23, 1967, Ser. No. 648,431

Int. Cl. H0111 71/16 U.S. Cl. 33755 13 Claims ABSTRACT OF THE DISCLOSURE Cross-reference to related application Certain parts of the herein disclosed circuit breaker are disclosed and claimed in our copending patent application Ser. No. 648,288, filed concurrently herewith.

Brief summary of the invention In the art of insulating-housing or molded-case type circuit breakers, the insulating housing is generally pro vided with an opening at the front thereof through which a handle extends to permit manual operation of the breaker. When the circuit breaker interrupts an overload or short circuit current the arc generates hot gases under pressure which gases are vented out of the housing through suitable venting means. During circuit interruption, particles of hot metal from the contacts or other metallic parts of the circuit-breaker mechanism are sometimes blown out of the breaker venting means. In order to prevent fire, it is desirable to prevent these hot gases and hot metallic particles from escaping through the front of the circuit breaker. These gases and/ or particles could, for example, ignite lint that tends to collect at the front of the breaker. Escaping hot gases and/ or metal particles at the front of the breaker could also burn an operator who might be about to manually operate the breaker at the time the tripping overload occurs. The circuit breaker of this invention is provided with improved means for sealing the handle opening. A molded insulating operating member comprises a shield part disposed generally within the housing and an integral handle part that extends outward through the front opening to permit manual operation of the breaker. The shield part comprises an arcuate surface that engages inner arcuate-surface means on the circuit breaker housing. The operating spring biases the operating member *frontward to bias the shield part of the operating member against the inner arcuate-surface means of the insulating housing. Upon occurrence of a tripping overload, the shield part of the operating member is biased, by the operating spring and also by means of the gas pressure within the housing, into tight engagement with the inner arcuate-surface means of the insulating housing to thereby seal the handle opening to limit the escape of arc-gases through the handle opening. The operating member is provided with molded pivot pins at the opposite sides thereof that are positioned in elongated openings in the sidewalls of the circuit-breaker housing. When it is desired to manually operate the circuit breaker, if the operator does not apply inward pressure to the handle, the operating member will ride on the inner arcuate-surface means of the housing during the manual operation. If the operator presses inward slightly on the Patented Oct. 28, 1969 handle, the operating member will float as it is pivoted in the elongated groove during the manual operation. If the operator presses firmly inward on the handle, the pivot pins will engage the lower surfaces of the openings in the sidewalls and pivot on these surfaces during the manual operation. In another embodiment of the invention a barrier is pivoted on the operating member to be forced into a sealing position by gas pressure in the housing upon the occurrence of circuit interruption to provide additional sealing means at the handle opening.

An object of this invention is to provide an improved circuit breaker with improved means for sealing off the handle-opening to limit the escape of arc-gases through the opening.

Another object of this invention is to provide an improved compact circuit breaker having an increased rating.

A general object of this invention is to provide an improved safer molded-case circuit breaker.

The invention, both as to structure and operation, together with additional objects and advantages thereof, will be best understood from the following detailed description when read in conjunction with the accompanying drawings.

In said drawings:

FIGURE 1 is a top plan view of a circuit breaker embodying principles of this invention;

FIG. 2 is a side view, with the side cover plate removed and with the arc-extinguishing structure shown in section, of the circuit breaker seen in FIG. 1;

FIG. 3 is a view similar to FIG. 2 with the parts shown in the tripped position;

FIG. 4 is a view of part of the housing seen in FIG. 2 with the operating member shown in broken lines;

FIG. 5 is a side elevational view of the operating member seen in FIG. 2;

FIG. 6 is a sectional view taken along the line VI-VI of FIG. 2, with parts being omitted for the purpose of clarity;

FIG. 7 is a partial view of the circuit breaker of FIG. 2 modified to provide a pivoted barrier in proximity to the handle opening; and

FIG. 8 is a view similar to FIG. 7 illustrating the position of the operating member and barrier during a tripping operation.

Referring to the drawings, there is shown, in FIGS. 1 and 2, a circuit breaker 3 comprising an insulating housing '5. The housing 5 comprises molded insulating housing part 7 and a molded insulating cover part 9. The housing part 7 is an open-sided member having a cavity into which the circuit breaker mechanism 11 is positioned during the assembly of the breaker. Thereafter, the cover part 9 is placed in position and three rivets are passed through three openings 13 (FIG. 2) in the housing parts 7 and 9 to secure the housing parts together. The circuit breaker housing 5 comprises a front 15 (FIG. 1), a back 17 (FIG. 2), two end walls 19 (FIG. 1) and two sidewalls 21.

The circuit breaker mechanism 11 comprises a stationary contact 23, a movable contact 25, an'operating mechanism 27, a trip device 29 and an arc-extinguishing structure 31.

The stationary contact 23 is fixedly secured to the inner end of a terminal conduct 33 that extends out through an opening 35 in the housing 5 and that is bent over to provide a generally fiat connecting part 37 having an opening 39 therein. When the circuit breaker is mounted on a panelboard, the part 37 of the terminal engages a flat conductor in the panelboard, and a bolt is passed through the opening 39 to fixedly secure the terminal 33 to the panelboard conductor. At the opposite end of the housing 5, a terminal conductor 41 extends out through an opening 43 in the housing 5 into a cavity as shown, and a screw-type solderless terminal connector 45 is connected to the outer end of the terminal 41 to permit connection of the terminal 41 to a conducting line at the panelboard installation. The terminal 45 is provided with a screw 47 for pressure connecting the conducting line to the terminal 41 in a manner well known in the art.

The movable contact 25 is fixedly secured to a conducting extension 49 that is fixedly secured to a U-shaped conducting contact arm 51. A molded insulating operating member or operating handle structure 53 is provided with a pair of pins 55 that are molded integral therewith. The pins 55 move in a pair of openings 57 in the opposite sidewalls of the housing in a manner to be hereinafter described. As can be seen in FIGS. 2 and 6, the upper ends of the legs of the U-shaped contact arm 51 pivotally engage the operating member 53 at pivot surfaces 59 that are provided in recesses in the oeprating member 53. The operating member 53 comprises an arcuate-shield part 61 and a handle part 63. As can be seen in FIGS. 1, 2 and 4, the insulating housing 5 is provided with an opening 65 at the front of the housing, and the operating member 53 is positioned at the opening with the handle part 63 protruding out through the opening and with the arcuate-shield part 61 closing the opening in all positions of the operating member 53. The front 15 of the insulating housing 5 is provided with inner surface means comprising a pair of arcuate surfaces 67 (FIG. 4) that are engaged by the arcuate shield part 61 of the operating member 53 in a manner to be hereinafter specifically described.

An overcenter operating spring 71 is connected, under tension, at the back end thereof in a suitable opening in the bright portion of the U-shaped switch arm 51 (FIG. 6) and at the front end thereof in a suitable spring opening in a spring support which is a trip member 73. The trip member 73 is pivotally supported at one end thereof in the sidewalls of the housing 5 by means of a pivot pin 75 (FIG. 2). The other end 77 of the trip member 73 extends into a window-opening in a latch member 79, and engages on a ledge in the window-opening of the member 79 in the latched position seen in FIG. 2.

The latch member 79 is a part of the trip device 29. The latch member 79 is an elongated metallic member having a pair of cars 81 (only one of which is seen in FIG. 2) at the opposite sides thereof that are positioned in V-shaped openings 83 in the opposite sidewalls of the housing 5 to pivotally support the member 79. A spring 85 biases the latch member 79 in a clockwise (FIG. 2) direction to the latching position seen in FIG. 2. The latch member 79 comprises an elongated latching leg 87 that is bent over at the lower end thereof to provide a short leg 89 that is positioned on the opposite side of one leg of a U-shaped bimetal 91 that is fixedly secured at one end thereof to the terminal conductor 41. A U-shaped magnetic member 93 is secured at the lower free end of the bimetal 91 with the opposite legs thereof facing an armature portion 95, of magnetic material, of the latch member 79. An insulating button 97 is fixed to the back of the U-shaped magnetic member 93 to engage the leg 89 of the latch member 7 9. An adjusting screw 99 is threaded into a nut 101 that is captured in the housing. The screw 99 can be rotated to adjust the initial position of the bimetal 91 to thereby calibrate the circuit breaker. A suitable cement may be used to close off the opening in back of the adjusting screw after the circuit breaker is calibrated.

In the closed position of the contacts, the circuit extends from the terminal 33 through the contact 23, the contact 25, the conducting extension 49, the contact arm 51, a flexible conductor 103 that is connected at one end to the contact arm 51 and at the other end to the lower free end of the bimetal 91, through the bimetal 91, the terminal 41, to a conducting line that would be connected to the terminal 41 by means of the solderless terminal connector 45.

The contacts are manually closed by counterclockwise movement of the operating member 53, in a manner to be hereinafter described, about the axis pivot pins 55 from the off to the on position. This movement, due to the pivotal engagement between the ends of the legs of the contact arm 51 with the pivot surfaces 59 of the operating member 53, toggles the upper end of the contact arm 51 to the right of the line of action of the spring 71 whereupon the spring 71, which has been additionally stretched during this movement, is positioned overcenter relative to the contact arm 51 and biases the contact arm 51 to the closed position with a snap-action. The contacts are manually opened by reverse movement of the operating member 53 from the on to the off position. This movement, through the pivotal engagement of ends of the legs of the contact arm 51 with pivot surfaces 59, toggles the upper end of the contact arm 51 to the left of the line of action of the spring 71, during which movement the spring 71 is additionally stretched, whereupon the spring 71 is positioned overcenter relative to the contact arm 51 and biases the contact arm 51 to the open position seen in FIG. 2 with a snap-action. Movement of the contact arm 51 to the open position is limited by the engagement of the contact arm with a projection 105 that is molded integral with the housing part 7.

When the circuit breaker 3 is in the closed position, and a persistent overload above a predetermined value of, for example, less than ten times normal rated current occurs, the trip device 29 operates thermally to effect a tripping operation. During this thermal tripping operation, which occurs with a time delay, the bimetal 91 flexes to the right, whereupon the insulating button 97 at the lower free end thereof engages the short leg 89 of the member 79 moving the member 79 in a counterclockwise direction about the pivots 81 to release the free end 77 of the releasable trip member 73. Upon release of the trip member 73, the spring 71 biases the trip member in a counterclockwise direction about the pivot 75 to a position wherein the trip member 77 engages the projection 105 on the circuit breaker housing. During this movement, the line of action of the spring 71 is moved from the left of the closed contact arm 51 to the right of the contact arm 51 and the spring 71 contracts to move the contact arm 51 to the tripped position seen in FIG. 3. During this movement, the spring 71 operates to move the operating member 53 to a tripped position intermediate the on and off positions to provide a visual indication, in a manner well known in the art, that the circuit breaker has tripped open. During this movement, an are drawn between the contacts 23 and 25 is extinguished in the arcextinguishing structure, and the arc gases escape through a vent passage 107 that leads out of one end of the circuit breaker and through another vent passage 109 that leads out the other end of the circuit breaker. The arc-extinguishing structure 31 and vent passages are more particularly described in our above-mentioned copending patent application Serial No. 648,288, filed concurrently herewith.

The circuit breaker is trip free in that the breaker will trip open even if the operating handle 63 is manually held in the on position.

When an overload current above ten times the normal rated current, or a short circuit current, occurs, the trip device 29 operates electromagnetically to trip the circuit breaker instantaneously. Upon the occurrence of the overload above ten times normal rated current, the current flowing through the bimetal 91 energizes the magnetic parts 93, 95 sufficiently so that the magnetic part 95 of the trip member 79 is attracted toward the magnetic member 93, independent of movement of the bimetal 91, to release the trip member 73. Upon release of the trip member 73 the circuit breaker is tripped open in the same manner as was hereinbefore ,described with regard to the thermal tripping operation.

After each tripping operation, the circuit breaker is reset and relatche'd by movement of the operating member 53 from the intermediate position to a position slightly past the full off" position. During this movement, a lower leg portion 110 of the operating member 53 engages a pin 111 on the trip member 73 to rotate the trip member 73 counterclockwise about the pivot 75. When the trip member 73 reaches the position seen in FIG. 2, the spring 85 biases the latch member 79 clockwise to the latching position shown. Thereafter, upon release of the operating member 53 the circuit breaker is latched. Thereafter, the circuit breaker can be operated in the same manner as was hereinbefore described.

In the on, off and tripped positions of the circuit breaker 3, the operating spring 71 is under tension between the trip member 73 and the contact arm 51. In these positions, the spring 71 tends to pull the trip member 73 downward (FIGS. 2 and 3) which movement is limited in the on and off positions because the trip member 73 is latched and which movement is limited in the tripped position (FIG. 3) because the trip member 73 engages the projection 105. Since the spring 71 is under tension in these positions, the spring pulls the contact arm 51 frontward, and because the switch arm 51 engages the surfaces 59 of the operating member 53, this force of the spring 71 operates through the contact arm 51 to bias the operating member 53 frontward where the arcuate shield part 61 of the operating member 53 engages the inner surface means or arcuate surfaces 67 (FIG. 4) of the front part of the insulating housing 5 at two opposite sides of the opening 65. The shield part 61 and the surfaces 67 form cooperating sealing means biased into cooperative sealing engagement by the operating spring 71. This movement is permitted because the openings 57 (FIG. 4) in the sidewalls 21 of the housing 5 are elongated in the direction from back to front and large enough to permit limited movement of the pivot pins 55 of the operating member 53 in the openings 57. During automatic tripping operations, the pressure of the arcgases that are generated in the arc-extinguishing structure 31 serves to additionally bias the operating member 53 into engagement with the surfaces 67 to provide increased sealing pressure even though the gas pressure is quickly relieved when the gases move out through the vent passages 107, 109. During an automatic tripping operation, the trip member 73, contact arm 51 and operating member 53 are moved to the tripped position .seen in FIG. 3 with the arcuate shield surface 61 of the operating member 53 riding along the arcuate surfaces 67 of the housing 5. During this movement the pressure within the housing and the operating spring 71 serve to bias the arcuate shield part 61 of the operating member 53 against the arcuate surfaces 67 of the housing 5 to limit passage of gases out through the front opening 65.

The manual operation can occur in three slightly different ways. If no downward pressure is applied to the operating member 53, the arcuate shield part 61 will ride along the arcuate surfaces 67 on the front of the housing moving about the axis of the pins 55 during the manual operations. If a limited amount of downward pressure is applied to the operating member 53, the operating member will essentially be moved away from the arcuate surfaces 67 and the member 53 will essentially float during the pivoting action about the axis of the pins 55 with the arcuate shield part 61 being spaced a slight ,distance from the surfaces 67 of the front of the housing. If an additional amount of downward pressure is applied to the operating member 53, the bottom surfaces of the pins 55 Will engage the bottom surfaces of the openings 57 (FIG. 4) Which surfaces limit downward movement of the operating member 53, and the operating member 53 will pivot about the lowered axis of the pins 55. During the automatic tripping operations, since there is no manual force being applied to the operating member 53, it can be understood that the arcuate shield surface 61 will ride against the arcuate surfaces 67 of the housing with the operating member 53 pivoting about the axis of the pins 55 which pins 55 will be in the upper position seen in FIG. 2.

As can be seen in FIGS. 4, 5 and 6, the operating member 53 is formed with arcuate surfaces 113 that are positioned close to, but spaced slightly from, arcuate surfaces 114 on the front of the housing. Although the surfaces 113, 114 do not engage when the operating member 53 is in the uppermost position, it can be understood with reference to FIG. 6 that gases and/or particles must move through a tortuous path to leave the housing at these areas. These surfaces 113, 114 are spaced very slightly because it is important that the surfaces 61, 67 engage. Because of manufacturing tolerances the slight spaces are provided between the surfaces 113, 114 to make sure that there will be no engagement between the surfaces 113, 114 that might interfere with the engagement between the surfaces 61, 67. Resilient packing or sealing material could be positioned between the member 53 and the housing front at the two sides of the handle opening opposite the two sides where the surfaces 67 are disposed.

Another embodiment of the invention is shown in FIGS. 7 and 8. In this embodiment an additional barrier 119 is mounted on the operating member 53 to provide an additional seal of the handle opening 65 on the side of the opening that is nearest the arc. In this embodiment, the circuit breaker is the same as that hereinbefore described with reference to FIGS. l-6; except that the barrier 119 is provided and the housing and operating members have been modified slightly to accommodate the use of the additional barrier 119. Thus, additional reference characters are applied only to the parts that are ne'cessary for an accurate description of this modification, it being understood that, unless otherwise specifically described, the circuit breaker is constructed in the same manner as the hereinbefore described circuit breaker. As can be seen in FIGS. 7 and 8, a metallic fiat barrier 119, which is slightly wider than the handle opening 65 seen in FIG. 1, is bent-over at one end 121 thereof to provide a hinge opening for receiving a pin 123that passes through the opening and that is fixed in the operating member 53 to pivotally support the barrier 119 on the operating member 53. The barrier member 119 may be either metallic or insulating. The shield part of the operating member has been formed with less material at 125 to accommodate movement of the barrier 119. The housing is provided with a cavity 127 in which the barrier 119 may move, and the barrier 119 engages a lower surface 129 of the cavity in the on and off positions. During movement of the operating member to the on and off positions, the barrier 119 merely pivots on the pivot pin 123. Upon the occurrence of an automatic tripping operation, when the operating member 53 moves to the intermediate positions seen in FIG. 8, the gas pressure hereinbefore described, that is generated by the arc, forces the barrier 119 upward into engagement with an upper surface 131 on the housing 5 to provide an additional seal for limiting the escape of gases through the handle opening. It can be understood that a similar barrier 119 could be similarly mounted at the other side of the handle opening to move in a similar cavity 127 at the other side of the handle opening to provide an additional sealing arrangement at the other side. The barrier 119 is preferably metal to absorb heat from the hot gases, and it can be understood that the barrier 119 is thin enough that there will be a slight flexing of the barrier underthe gas pressure against the surface 131 to provide a good sealing arrangement. I

From the foregoing, it can be understood that there is provided by this invention an improved circuit breaker wherein the operating spring biases an arcuate shield part of the operating member frontward into engagement with arcuate surfaces on the front part of the insulating housing to limit the passage of gases out through the handle opening. A pair of pins molded integral with the insulating operating member at opposite sides of the operating member are positioned in openings in the sidewalls of the housing which openings are enlarged to permit engagement of the shield with the housing. During manual operation the pins can float in the opening if a slight downward pressure is applied to the operating member, and if firm pressure is applied the pins will pivotally engage arcuate lower surfaces in the opening in the sidewalls. When the circuit breaker trips in response to an overload the operating member moves to an intermediate position intermediate the on and off positions to provide a visual indication that the circuit breaker has tripped, and the operating spring, along with the gas pressure within the circuit breaker housing, serve to bias the arcuate shield into engagement with the arcuate surfaces of the front of the housing. In another embodiment of the invention, a barrier, which is pivotally connected to the operating member, is forced into sealing engagement with the front of the housing by gas pressures within the housing when the circuit breaker trips open.

Since numerous changes may be made in the abovedescribed construction and because different embodiments of the invention may be made without departing from the spirit and scope of the invention, it is intended that all of the matter contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

We claim as our invention:

1. A circuit breaker comprising an insulating housing, said insulating housing comprising a front having an opening therein, said front comprising inner surface means in proximity to said opening, a circuit breaker mechanism supported in said insulating housing, said mechanism comprising a stationary contact, a movable contact arm having a movable contact thereon cooperable with said stationary contact, an operating member comprising a shield part closing said opening and a handle part extending through said opening for manual operation, a spring support, an operating spring supported between said spring support and said contact arm, said operating spring biasing said contact arm frontward to bias said contact arm into pivotal engagement with said operating member and to operate through said contact arm to bias said operating member frontward to thereby bias said shield part into engagement with said inner surface means of said front of said insulating housing, said operating member being movable between two positions to toggle said contact arm and to operate said operating spring to move said contact arm between open and closed positions.

2. A circuit breaker according to claim 1, said inner surface means of said front of said insulating housing comprising arcuate inner surface means, said operating member comprising an insulating member with said shield part and said handle part molded as an integral unit, and said shield part comprising arcuate surface means engaging said inner arcuate surface means of said front of said insulating housing.

3. A circuit breaker according to claim 2, said insulating housing comprising a pair of sidewalls having a pair of oppositely disposed pivot openings therein, said operating member comprising a pair of pivot pin-s at opposite sides thereof molded integral therewith, said pivot pins being positioned in said pivot openings, said pivot openings being large enough to permit said arcuate surface means of said shield to engage said arcuate inner surface means of said front of said housing insulating, said pair of sidewalls at said pair of pivot openings comprising bottom pivot surfaces, and upon the application of downward pressure on said operating member said pivot pins pivotally engaging said bottom pivot surfaces to pivotally support said operating member for pivotal movement.

4. A circuit breaker according to claim 1, said contact arm extending generally from front to back in said insulating housing and carrying said movable contact at the back part thereof, said spring support being a trip member pivotally supported at one end thereof, trip means latching said trip member at the other end of said trip member, said operating spring comprising a tension spring connected at the back part thereof to said contact arm and at the front part thereof to said trip member, said contact arm at the front part thereof pivotally engaging said operating member whereby said tension spring biases said contact arm toward said front to bias said operating member toward said front to thereby bias said shield part into engagement with said inner surface means of said front of said insulating housing.

5. A circuit breaker according to claim 4, said inner surface means of said front of said insulating housing comprising arcuate inner surface means, said operating member comprising a molded insulating member with said shield part and handle part molded as an integral unit, and said shield part comprising arcuate surface means engaging said arcuate inner surface means of said front of said insulating housing.

6. A circuit breaker according to claim 5, upon the occurrance of an overload current above a predetermined value said trip means releasing said trip member and said operating spring operating to pivot said trip member to a tripped position during which movement said operating spring operates to move said contact arm to the open positon and during which movement said operating spring operates to move said operating member to a tripped position intermediate said two positions to provide a visual indication that said circuit breaker has tripped, and upon the occurrence of said tripping operation said operating spring and the gases generated by an arc established between said contacts cooperating to bias said operating member toward said front to thereby bias said arcuate surface means of said shield part into engagement with said arcuate inner surface means of said front of said insulating housing.

7. A circuit breaker according to claim 6, said insulating housing comprising a pair of sidewalls having oppositely disposed pivot openings therein, said operating member comprising a pair of pivot pins molded integral therewith at opposite sides thereof, said opposite pivot pins being disposed in said oppositely disposed pivot openings, said pivot openings being large enough relative to said pivot pins to permit said arcuate surface means of said shield part to engage said arcuate inner surface means of said front of said insulating housing, said pivot openings comprising bottom pivot surface means, and upon downward pressure against said operating member said pivot pins engaging said bottom pivot surface means to support said operating member for pivotal movement.

8. A circuit breaker according to claim 6, a barrier member pivotally connected to said operating member within said insulating housing, and upon the occurrence of said tripping operation said gas pressure forcing said barrier member against additional inner surface means of said front of said insulating housing.

9. A circuit breaker comprising an insulating housing comprising a front having an opening therein, a circuit breaker mechanism supported in said insulating housing, said circuit breaker mechanism comprising a stationary contact, a movable contact, a contact arm carrying said movable contact, a releasable trip member, trip means latching said releasable trip member, an operating spring connected between said releasable trip member and said contact arm, an operating member comprising a shield part closing said opening and a handle part extending through said opening for manual operation, said operating member being movable pivotally between two operating positions to operate said contact arm and operating spring to open and close said contacts, said trip means operating upon the occurrence of overload current conditions above a predetermined value to release said releasable trip member, upon release of said releasable trip member said operating spring operating to move said releasable trip member to a tripped position during which movement said operating spring operates to move said contact arm to an open position and to move said operating member to a tripped position intermediate said two operating positions, a barrier member pivotally connected to said operating member within said insulating housing, and upon the occurrence of said automatic tripping operation the pressure generated by are gases forcing said barrier to pivotally move said barrier into engagement with an inner surface of the front of said insulating housing to block the passage of gases through said handle opening.

10. A circuit breaker according to claim 9, and said barrier comprising a flexible metallic barrier member.

11. A circuit breaker comprising an insulating housing, said insulating housing comprising a front having an opening therein, a circuit breaker mechanism supported in said insulating housing, said mechanism comprising a stationary contact, a movable contact arm having a movable contact thereon cooperable with said stationary contact, an operating handle structure comprising a handle part extending frontward through said opening for manual operation, positions to operate said operating spring to open and cooperating sealing means on said insulating housing and said operating handle structure, a spring support, an operating spring supported between said spring support and said contact arm, said operating spring biasing said -cntact arm frontward to bias said contact arm into pivotal engagement with said operating handle structure and to operate through said contact arm to bias said operating handle structure frontward to thereby bias said cooperating sealing means into cooperative sealing engagement, and said operating handle structure, being movable between two positions to toggle said contact arm and to operate said operating spring to move said contact arm between open and closed positions.

12. A circuit breaker according to claim 11, said contact arm extending generally from front to back in said insulating housing and carrying said movable contact at the back part thereof, said spring support being a trip member pivotally supported at one end thereof, trip means latching said trip member at the other end of said trip member, said operating spring comprising a tension spring connected at the back part thereof to said contact arm and at the front part thereof to said trip member, said contact arm at the front part thereof pivotally engaging said operating handle structure whereby said tension spring biases said contact arm toward said front to bias said operating handle structure toward said front to thereby bias said cooperating sealing means into said cooperative sealing engagement.

13. A circuit breaker according to claim 12, said insulating housing having a pair of spaced oppositely disposed pivot openings therein, said operating handle structure comprising a pair of pivot pins at opposite sides thereof, said pivot pins being positioned in said pivot openings, said pivot openings being large enough to permit frontward movement of said operating handle structure to the position where said cooperating sealing means is in said cooperative sealing engagement, said insulating housing at said pair of pivot openings comprising bottom pivot surfaces,- and upon the application of manual downward pressure on said operating handle structure against the bias of said tension spring said pivot pins pivotally engaging said bottom pivot surfaces to pivotally support said operating handle structure for pivotal movement.

References Cited UNITED STATES PATENTS 2,659,783 11/1953 Casey 337 X 3,088,008 4/1963 Gelzheiser 33755 X 3,311,724 3/ 1967 Powell 337-55 2,878,347 3/1959 Schmidt.

3,211,877 10/1965 Walker et a1.

3,287,522 11/1966 Casey 200-116 3,341,791 9/1967 Leonard.

BERNARD A. GILHEANY, Primary Examiner H. B. GILSON, Assistant Examiner US. Cl. X.R. 337-227 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 475 710 Dated June 23 1967 lnventofls) James P. Ellsworth et a1 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 3, line 9 cancel "housing insulating" and substitute insulating housing Claim 11, lines 9 and 10, cancel "positions to operate said operating spring to open and".

SIGNED AN; QEALED WEI-1m (SEAL) mmnmm. I. a Oomiasiom o1 Patzdtll 

